Damper device

ABSTRACT

A damper device including an input element to which power from a motor is transmitted; a first elastic body to which power is transmitted from the input element; a first intermediate element to which power is transmitted from the first elastic body; a second elastic body to which power is transmitted from the first intermediate element; a second intermediate element to which power is transmitted from the second elastic body; a third elastic body to which power is transmitted from the second intermediate element; and an output element to which power is transmitted from the third elastic body. The first and second elastic bodies are coil springs, and the third elastic body is an arc spring that is arranged radially inward of the first and second elastic bodies.

The disclosure of Japanese Patent Application No. 2011-029714 filed onFeb. 15, 2011 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a damper device that includes an inputelement to which power is transmitted from a motor, a first intermediateelement to which power is transmitted from the input element via a firstelastic body, a second intermediate element to which power istransmitted from the first intermediate element via a second elasticbody, and an output element to which power is transmitted from thesecond intermediate element via a third elastic body.

DESCRIPTION OF THE RELATED ART

There is known an existing damper device of this type, which includesfirst elastic members that are provided on a piston of a lock-up device,second elastic members that are provided on a driven plate fixed to aturbine runner of a torque converter, and an intermediate member that iscoupled to the piston in a rotation direction via the first elasticmembers and that is coupled to the driven plate in the rotationdirection via the second elastic members (for example, see JapanesePatent Application Publication No. 2001-82577). In this damper device,the second elastic members each are formed of a pair of coil springs andan intermediate float body that is arranged between the pair of coilsprings, and each pair of coil springs are caused to act in series witheach other to thereby increase the torsional angle (provide longstroke).

SUMMARY OF THE INVENTION

In the existing damper device described above, the second elasticmembers each are formed of a pair of coil springs and an intermediatefloat body that is arranged between the pair of coil springs to therebyprovide long stroke; however, part of the elastic members thatconstitute the damper device are formed of an arc spring to thereby makeit possible to provide further long stroke (low stiffness) for thedamper device. However, an arc spring has a hysteresis higher than thatof a coil spring, so, when an arc spring is applied to the damperdevice, it is necessary to make consideration so as not to impair thevibration damping effect of the arc spring because of the hysteresis.

Thus, it is a main object of the present invention to improve thevibration damping characteristic while providing long stroke for thedamper device using an arc spring.

The damper device according to the present invention employs thefollowing means for achieving the above main object.

A damper device according to an aspect of the present inventionincludes: an input element to which power from a motor is transmitted; afirst elastic body to which power is transmitted from the input element;a first intermediate element to which power is transmitted from thefirst elastic body; a second elastic body to which power is transmittedfrom the first intermediate element; a second intermediate element towhich power is transmitted from the second elastic body; a third elasticbody to which power is transmitted from the second intermediate element;and an output element to which power is transmitted from the thirdelastic body. In the damper device, the first and second elastic bodiesare coil springs and the third elastic body is an arc spring that isarranged radially inward of the first and second elastic bodies.

The damper device includes the input element to which power istransmitted from the motor, the first intermediate element to whichpower is transmitted from the input element via the first elastic body,the second intermediate element to which power is transmitted from thefirst intermediate element via the second elastic body, and the outputelement to which power is transmitted from the second intermediateelement via the third elastic body. Then, in this damper device, coilsprings are used as the first and second elastic bodies, and an arcspring that is arranged radially inward of the first and second elasticbodies is used as the third elastic body. In this way, the third elasticbody, which is one of the serially arranged elastic bodies, is an arcspring, so it is possible to provide long stroke (low stiffness) for thedamper device. In addition, the third elastic body that is an arc springis arranged radially inward of the first and second elastic bodies toreduce centrifugal force that acts on the third elastic body to therebyreduce the hysteresis of the third elastic body, that is, friction forcethat acts on the third elastic body during a reduced load. By so doing,it is possible to appropriately maintain the vibration dampingcharacteristic of the third elastic body. Thus, in this damper device,it is possible to improve the vibration damping characteristic whileproviding long stroke using an arc spring.

In addition, the input element may have a contact portion that contactswith one end of the first elastic body, the first intermediate elementmay have a contact portion that is arranged between the other end of thefirst elastic body and one end of the second elastic body adjacent tothe first elastic body and that contacts with both, the secondintermediate element may have a contact portion that slidably supportsthe third elastic body and that contacts with the other end of thesecond elastic body and a contact portion that contacts with one end ofthe third elastic body, and the output element may have a contactportion that contacts with the other end of the third elastic body.

Furthermore, a stiffness of the first elastic body may be higher thanstiffnesses of the second and third elastic bodies. That is, in theabove damper device, the first intermediate element and the secondintermediate element are arranged between the first elastic body and thethird elastic body, so the first intermediate element and the secondintermediate element may resonate. In contrast to this, when thestiffness of the first elastic body is set so as to be higher than thestiffness of the second elastic body, this makes it easy tosubstantially integrate the first intermediate element with the secondintermediate element, and the resonance frequency of the firstintermediate element and second intermediate element is increased bysetting the stiffness of the first elastic body so as to be relativelyhigh, so it is possible to cause resonance between the firstintermediate element and the second intermediate element when therotation speed of the input element is relatively high, that is, whenthe rotation speed of the motor is relatively high, and torque(vibrating force) from the motor is relatively low. By so doing, it ispossible to suppress an increase in the vibration level of the damperdevice as a whole due to resonance between the first intermediateelement and the second intermediate element. Then, when the stiffness ofthe first elastic body is set so as to be higher than the stiffness ofthe third elastic body, the characteristic of the arc spring that is thethird elastic body is utilized to improve the vibration dampingcharacteristic while providing the long stroke (low stiffness) for thedamper device, and it is possible to appropriately damp resonancebetween the first intermediate element and the second intermediateelement by the third elastic body.

In addition, the input element may be connected via a lock-up clutch toan input member coupled to the motor, and the output element may becoupled to an input shaft of a transmission. That is, the above damperdevice is able to improve the vibration damping characteristic whileproviding long stroke (low stiffness) using an arc spring. Thus, byusing the above damper device, when the rotation speed of the motor isextremely low, it is possible to carry out lockup by the lock-up clutch,that is, couple the input member to the input shaft of the transmission,while appropriately reducing transmission of vibrations from the inputmember to the input shaft of the transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cross-sectional view that shows a fluidtransmission apparatus 1 that includes a damper device 10 according toan embodiment of the present invention;

FIG. 2 is a configuration diagram that shows the damper device 10;

FIG. 3 is a schematic configuration diagram of the fluid transmissionapparatus 1; and

FIG. 4 is an explanatory graph that illustrates the correlation betweenthe rotation speed of an engine, which serves as a motor, and thevibration level of the damper device 10.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A mode for carrying out the present invention will now be describedusing an embodiment.

FIG. 1 is a configuration diagram that shows a fluid transmissionapparatus 1 that includes a damper device 10 according to the embodimentof the present invention. The fluid transmission apparatus 1 shown inthe drawing is a torque converter that is mounted as a startingapparatus on a vehicle equipped with an engine (internal combustionengine) that serves as a motor. The fluid transmission apparatus 1includes: a front cover (input member) 3 that is coupled to a crankshaftof the engine (not shown); a pump impeller (input-side fluidtransmitting element) 4 that is fixed to the front cover 3; a turbinerunner (output-side fluid transmitting element) 5 that is rotatablecoaxially with the pump impeller 4; a stator 6 that rectifies the flowof hydraulic oil (hydraulic fluid) from the turbine runner 5 to the pumpimpeller 4; a damper hub (output member) 7 that is fixed to an inputshaft of a transmission (not shown), which is an automatic transmission(AT) or a continuously variable transmission (CVT); a friction-typesingle disc lock-up clutch mechanism 8 that has a lock-up piston 80; andthe damper device 10 that is connected to the damper hub 7 and that isconnected to the lock-up piston 80.

The pump impeller 4 has a pump shell 40 that is airtightly fixed to thefront cover 3 and a plurality of pump blades 41 that are arranged on theinner surface of the pump shell 40. The turbine runner 5 has a turbineshell 50 and a plurality of turbine blades 51 that are arranged on theinner surface of the turbine shell 50. The turbine shell 50 is fitted tothe damper hub 7, and is fixed to the damper hub 7 via rivets. Thestator 6 has a plurality of stator blades 60. The rotation direction ofthe stator 6 is set in only one direction by a one-way clutch 61. Thepump impeller 4 and the turbine runner 5 face each other, and these pumpimpeller 4, turbine runner 5 and stator 6 form a torus (annular flowpassage) that circulates hydraulic oil.

As shown in FIG. 1 and FIG. 2, the damper device 10 includes: a drivemember 11 that serves as an input element; a first intermediate member(first intermediate element) 12 that engages with the drive member 11via a plurality of first springs (first elastic bodies) SP1; a secondintermediate member (second intermediate element) 14 that engages withthe first intermediate member 12 via a plurality of second springs(second elastic bodies) SP2; and a driven member (output element) 15that engages with the second intermediate member 14 via a plurality ofthird springs (third elastic bodies) SP3. In the embodiment, the firstand second springs SP1 and SP2 each are a coil spring made of a metalmaterial wound in a spiral shape so as to have an axis extending in astraight line when no load is applied, and the third springs SP3 eachare an arc spring made of a metal material wound so as to have an axisextending in a circular arc shape when no load is applied.

The drive member 11 has a plurality of spring contact portions 11 a,which are respectively in contact with one ends of the correspondingfirst springs SP1, and a plurality of spring support portions 11 b.Then, the drive member 11 is fixed to the lock-up piston 80 of thelock-up clutch mechanism 8 via rivets, and is arranged in the outerperipheral region of a housing inner space defined by the front cover 3and the pump shell 40 of the pump impeller 4. The first intermediatemember 12 is formed as an annular member that is able to slidablysupport the first and second springs SP1 and SP2 together with theplurality of spring support portions 11 b of the drive member 11. In theembodiment, the first intermediate member 12 is rotatably supportedaround the axis of the fluid transmission apparatus 1 by the secondintermediate member 14 and is arranged in the outer peripheral region ofthe housing inner space. In addition, as shown in FIG. 1 and FIG. 2, thefirst intermediate member 12 has a plurality of spring contact portions12 a that are respectively arranged between the other ends of thecorresponding first springs SP1 and one ends of the second springs SP2adjacent to the first springs SP1 and that are respectively in contactwith both.

The second intermediate member 14 is formed of an annular first plate141 and an annular second plate 142 that is fixed to the first plate 141via rivets. In the embodiment, the second intermediate member 14 isrotatably supported around the axis of the fluid transmission apparatus1 by the driven member 15. The first plate 141 of the secondintermediate member 14 has, at its outer peripheral side, a plurality ofspring contact portions 141 a that are respectively in contact with theother ends of the corresponding second springs SP2 and a plurality ofsupport portions 141 b that rotatably support the inner peripheralportion of the first intermediate member 12, and has, at its innerperipheral side, a plurality of spring support portions for supportingthe third springs SP3. In addition, the second plate 142 of the secondintermediate member 14 has spring support portions that respectivelyface the spring support portions of the first plate 141 to support thethird springs SP3. Then, a plurality of spring contact portions 141 c(see FIG. 2) that are respectively in contact with one ends of thecorresponding third springs SP3 are formed in the first and secondplates 141 and 142.

By so doing, the plurality of first springs SP1 are arranged at theouter peripheral portion of the damper device 10 so as to berespectively positioned between the spring contact portions 11 a of thedrive member 11 and the spring contact portions 12 a of the firstintermediate member 12, and the plurality of second springs SP2 arearranged at the outer peripheral portion of the damper device 10 so asto be respectively positioned between the spring contact portions 12 aof the first intermediate member 12 and the second intermediate member14, that is, the spring contact portions 141 a of the first plate 141.In addition, the plurality of third springs SP3 each are arranged so asto be spaced apart from the first and second springs SP1 and SP2 in theradial direction of the fluid transmission apparatus 1, and arepositioned radially inward of the first and second springs SP1 and SP2.

The driven member 15 is arranged between the first plate 141 and secondplate 142 of the second intermediate member 14, and is fixed to thedamper hub 7. In addition, the driven member 15 has a plurality ofspring contact portions 15 a that are respectively in contact with theother ends of the corresponding third springs SP3. Furthermore, thedriven member 15 has a plurality of circular arc slits 15 d that areengaged with protrusions 141 d extending from the inner peripheralportion of the first plate 141 of the second intermediate member 14 inthe axial direction of the fluid transmission apparatus 1. When theprotrusions 141 d of the first plate 141 are engaged with (looselyfitted to) the corresponding slits 15 d of the driven member 15, thesecond intermediate member 14 is supported by the driven member 15 andarranged around the axis of the fluid transmission apparatus 1 so as tobe rotatable with respect to the driven member 15 within the rangecorresponding to the perimeter of each slit 15 d.

The lock-up clutch mechanism 8 is able to carry out lockup for couplingthe front cover 3 to the damper hub 7 via the damper device 10 and torelease the lockup. In the embodiment, as shown in FIG. 1, the lock-uppiston 80 of the lock-up clutch mechanism 8 is arranged inside the frontcover 3 and near the inner wall surface, adjacent to the engine (rightside in the drawing), of the front cover 3, and is fitted to the damperhub 7 so as to be slidable in the axial direction and rotatable withrespect to the damper hub 7. In addition, a friction material 81 isstuck to the outer periphery of the surface on the front cover 3 side ofthe lock-up piston 80. Then, a lock-up chamber 85 that is connected to ahydraulic control unit (not shown) via an oil passage fanned in ahydraulic oil supply hole (not shown) and the input shaft is definedbetween the back surface (right side surface in the drawing) of thelock-up piston 80 and the front cover 3.

When power is transmitted between the pump impeller 4 and the turbinerunner 5 without carrying out lockup of the lock-up clutch mechanism 8,hydraulic oil supplied to the pump impeller 4 and the turbine runner 5flows into the lock-up chamber 85, and the lock-up chamber 85 is filledwith hydraulic oil. Thus, at this time, the lock-up piston 80 is notmoved toward the front cover 3, so the lock-up piston 80 is notfrictionally engaged with the front cover 3. Then, during lock-uprelease where lockup is not carried out by the lock-up clutch mechanism8 in this way, as is apparent from FIG. 3, power from the engine thatserves as a motor is transmitted to the input shaft of the transmissionvia a path formed of the front cover 3, the pump impeller 4, the turbinerunner 5 and the damper hub 7.

In addition, when the pressure inside the lock-up chamber 85 is reducedby the hydraulic control unit (not shown), the lock-up piston 80 ismoved toward the front cover 3 because of the pressure difference and isthen frictionally engaged with the front cover 3. By so doing, the frontcover 3 is coupled to the damper hub 7 via the damper device 10. Duringlockup where the front cover 3 is coupled to the damper hub 7 by thelock-up clutch mechanism 8 in this way, power from the engine thatserves as a motor is transmitted to the input shaft of the transmissionvia a path formed of the front cover 3, the lock-up clutch mechanism 8,the drive member 11, the first springs SP1, the first intermediatemember 12, the second springs SP2, the second intermediate member 14,the third springs SP3, the driven member 15 and the damper hub 7, as isapparent from FIG. 3. At this time, fluctuations (vibrations) in torqueinput to the front cover 3 are absorbed by the first, second and thirdsprings SP1, SP2 and SP3 of the damper device 10.

Then, in the fluid transmission apparatus 1 of the embodiment, lockup iscarried out by the lock-up clutch mechanism 8 at the time when therotation speed of the engine coupled to the front cover 3 has reached anextremely low lock-up rotation speed Nlup, that is, for example, about1000 rpm. By so doing, power transmission efficiency between the engineand the transmission is improved to thereby make it possible to furtherimprove the fuel economy of the engine. Note that, when reducing thepressure inside the lock-up chamber 85 is stopped, the lock-up piston 80separates from the front cover 3 because of a reduction in pressuredifference resulting from the flow of hydraulic oil into the lock-upchamber 85. By so doing, lockup is released.

In this way, in order to carry out lockup at the time when the rotationspeed of the engine has reached the extremely low lock-up rotation speedNlup, that is, for example, about 1000 rpm, it is necessary toappropriately damp vibrations by the damper device 10 between the engineand the transmission when the rotation speed of the engine falls withina low rotation speed range near the above described lock-up rotationspeed Nlup. Therefore, in the damper device 10 of the embodiment, inorder to improve the vibration damping characteristic, arc springs areused as the third springs SP3 among the serially arranged first to thirdsprings SP1 to SP3 to provide further long stroke (low stiffness).However, each arc spring has a hysteresis higher than that of each coilspring, so, in the damper device 10 of the embodiment, the thin springsSP3, which are arc springs, are arranged radially inward of the firstand second springs SP1 and SP2 such that the hysteresis does not impairthe vibration damping effect of the third springs SP3 that are arcsprings. By so doing, centrifugal force that acts on the third springsSP3 is reduced to reduce the hysteresis of the third springs SP3, thatis, friction force that acts on the third springs SP3 during a reducedload to thereby make it possible to appropriately maintain the vibrationdamping characteristic of the third springs SP3.

On the other hand, in the fluid transmission apparatus 1 of theembodiment, the first and second intermediate members 12 and 14, whichserve as the intermediate elements, are arranged between the firstsprings SP1 and third springs SP3 of the damper device 10, so the firstintermediate member 12 and the second intermediate member 14 mayresonate. Then, resonance between the first intermediate member 12 andthe second intermediate member 14 occurs when the rotation speed of theengine, for example, falls within a low rotation speed range near theabove described lock-up rotation speed Nlup and the vibration level ofthe damper device 10 as a whole (driven member 15 serving as the outputelement) is relatively high, the vibration level of the damper device 10as a whole further increases because of the resonance between the firstintermediate member 12 and the second intermediate member 14, andrelatively large vibrations may be transmitted to the downstream side ofthe damper device 10, that is, the input shaft of the transmission.Thus, in order to smoothly carry out lockup by the lock-up clutchmechanism 8 at the time when the rotation speed of the engine hasreached the extremely low lock-up rotation speed Nlup, it is better tocause resonance between the first intermediate member 12 and the secondintermediate member 14 when the rotation speed of the engine aftercompletion of lockup is relatively high and torque, that is, vibratingforce, from the engine is relatively low.

Here, the state where the first and second intermediate members 12 and14 substantially integrally resonate corresponds to a state where thefirst springs SP1 and the third springs SP3 are connected in parallelwith the first and second intermediate members 12 and 14, which serve asa single mass. In this case, when the spring constant of each firstspring SP1 is “k1” and the spring constant of each third spring SP3 is“k3”, the resultant spring constant k₁₃ of the system is “k1+k3”, so theresonance frequency (natural frequency) fi of the first and secondintermediate members 12 and 14 that substantially integrally resonate isexpressed as fi=1/2π·√{(k1+k3)/I} (where “I” is the sum of the inertiaof the first intermediate member 12, the inertia of the secondintermediate member 14 and the inertia of the second springs SP2. Notethat the unit of the inertia I is “kg·m2”). In addition, when the damperdevice 10 as a whole integrally resonates, the drive member 11, thefirst springs SP1, the first intermediate member 12, the second springsSP2, the second intermediate member 14, the third springs SP3 and thedriven member 15 are coupled in series with one another, so theresultant spring constant k₁₂₃ of the system is expressed by1/k₁₂₃=1/k1+1/k2+1/k3 where the spring constant of each second springSP2 is “k2”, and the resonance frequency ft of the damper device 10 as awhole is expressed by ft=1/2π·√(k₁₂₃/It) (where It is the inertia of thedamper device as a whole).

Thus, in order to cause resonance between the first intermediate member12 and the second intermediate member 14 when the rotation speed of theengine after completion of lockup is relatively high, it is better toincrease the sum of the spring constant k1 of each first spring SP1 andthe spring constant k3 of each third spring SP3 as much as possible soas to further increase the resonance frequency fi of the first andsecond intermediate members 12 and 14. In addition, in order to causethe resonance of the damper device 10 as a whole at the time when therotation speed of the engine before completion of lockup is relativelylow, it is better to reduce the resultant spring constant k₁₂₃ of thesystem as much as possible so as to further decrease the resonancefrequency ft of the damper device 10 as a whole.

In consideration of the above, in the damper device 10 of theembodiment, the stiffness of each first spring SP1 is set so as to behigher than the stiffness of each second spring SP2 and the stiffness ofeach third spring SP3. That is, in the present embodiment, the springconstant k1 of each first spring SP1 is set so as to be much larger (forexample, about several times) than the spring constant k2 of each secondspring SP2 and the spring constant k3 of each third spring SP3. When thestiffness of each first spring SP1 is set so as to be higher than thestiffness of each second spring SP2 in this way, this makes it easy tosubstantially integrate the first intermediate member 12 with the secondintermediate member 14, and the resonance frequency fi of the first andsecond intermediate members 12 and 14 is increased by setting thestiffness of each first spring SP1 so as to be relatively high, so it ispossible to cause resonance between the first intermediate member 12 andthe second intermediate member 14 when the rotation speed of the engineis relatively high and torque (vibrating force) from the engine isrelatively low. Furthermore, when the stiffness of each first spring SP1is set so as to be higher than the stiffness of each third spring SP3,the characteristic of the arc springs that are the third springs SP3 isutilized to improve the vibration damping characteristic while providingthe long stroke (low stiffness) for the damper device 10, and it ispossible to appropriately damp resonance between the first intermediatemember 12 and the second intermediate member 14 by the third springsSP3. Then, in the damper device 10 of the embodiment, in order toutilize the characteristic of an arc spring such that the stiffness maybe easily decreased as compared with a coil spring and to furtherappropriately maintain the vibration damping characteristic of the thirdsprings SP3, which are arc springs, arranged radially inward of thefirst and second springs SP1 and SP2 so as to reduce hysteresis, thespring constant k3 (stiffness) of each third spring SP3 is set so as tobe smaller than the spring constant k2 (stiffness) of each second springSP2. That is, by setting the spring constants (stiffnesses) of the firstto third springs SP1 to SP3 such that k1>k2>k3 (k1>>k2>k3), theresonance frequency fi of the first and second intermediate members 12and 14 is increased while the resonance frequency ft of the damperdevice 10 as a whole is decreased, and the stiffness of each thirdspring SP3 is decreased to thereby make it possible to improve thevibration damping characteristic of the damper device 10 as a whole.

Note that, here, the “stiffness” and the “spring constant” each indicate“force (torque)/torsional angle (the unit is “Nm/rad” or “Nm/deg”)”, andare synonymous with each other. In addition, the stiffness (springconstant) of a spring decreases (reduces) by reducing the wire diameterof the spring or reducing the number of turns per unit length, andincreases by increasing the wire diameter of the spring or increasingthe number of turns per unit length.

FIG. 4 is an explanatory graph that illustrates the correlation betweenthe rotation speed of the engine and the vibration level of the abovedescribed damper device 10. The graph illustrates the correlationbetween the rotation speed of the engine (front cover 3) and thevibration level in the driven member 15 (damper hub 7), which serves asthe output element of the damper device, in a plurality of damperdevices, including the damper device 10 of the embodiment, obtainedthrough simulations of a torsional vibration system. In the abovesimulations, the specifications of the damper device 10, other than thespecifications of the engine that serves as a motor, the specificationsof the pump impeller 4, turbine runner 5 and lock-up clutch mechanism 8and the specifications of the first to third springs SP1 to SP3, arebasically the same, and the types and stiffnesses of the first to thirdsprings SP1 to SP3 are varied.

The solid line in FIG. 4 indicates the vibration level of the damperdevice 10 of the above embodiment. In addition, the alternate long andshort dash line in FIG. 4 indicates the vibration level of a damperdevice of a first alternative embodiment in which, in the damper device10 of the embodiment, the spring constant k3 of each third spring SP3 isset so as to be smaller than the spring constant k1 of each first springSP1 and is set so as to be larger than the spring constant k2 of eachsecond spring SP2 (k1>k3>k2 (k1>>k3>k2)). Furthermore, the alternatelong and two short dashes line in FIG. 4 indicates the vibration levelof a damper device of a second alternative embodiment in which, in thedamper device 10 of the embodiment, all the first to third springs SP1to SP3 are coils springs and the spring constants of the first to thirdsprings SP1 to SP3 are set such that k1>k2>k3 (k1>>k2>k3) as in the caseof the damper device 10. Then, the broken line in FIG. 4 indicates thevibration level of a damper device of a comparative embodiment in which,in the damper device 10 of the embodiment, all the first to thirdsprings SP1 to SP3 are coil springs and the spring constants of thefirst to third springs SP1 to SP3 are the same (k1=k2=k3).

As is apparent from FIG. 4, in the damper device 10 of the embodimentand the damper device of the first alternative embodiment, as comparedwith the damper device of the comparative embodiment, the resonancefrequency of the first and second intermediate members 12 and 14increases, so resonance between the first intermediate member 12 and thesecond intermediate member 14 occurs at the time when the rotation speedof the engine is relatively high. Then, as is apparent from comparisonwith the comparative embodiment, in the damper device 10 of theembodiment and the damper device of the first alternative embodiment,arc springs used as the third springs SP3 in order to provide longstroke (low stiffness) are arranged radially inward of the first andsecond springs SP1 and SP2 so as to reduce hysteresis, so it is possibleto further appropriately damp resonance between the first intermediatemember 12 and the second intermediate member 14, which occurs at thetime when the rotation speed of the engine is further increased.

In addition, in the damper device 10 of the embodiment and the damperdevice of the first alternative embodiment, as compared with the damperdevice of the comparative embodiment, the resonance of the damper deviceas a whole occurs at the time when the rotation speed of the engine islower before completion of lockup because of a decrease in the resonancefrequency of the damper device as a whole. Thus, the vibration level atthe time when the rotation speed of the engine is near the lock-uprotation speed Nlup further decreases. Thus, in the damper device 10 ofthe embodiment and the damper device of the first alternativeembodiment, it is possible to exceedingly smoothly carry out lockup bythe lock-up clutch mechanism 8 at the time when the rotation speed ofthe engine has reached the extremely low lock-up rotation speed Nlup.

Furthermore, when the damper device 10 of the embodiment is comparedwith the damper device of the first alternative embodiment, in thedamper device of the first alternative embodiment, the spring constantk3 of each third spring SP3 is set so as to be larger than the springconstant k2 of each second spring SP2, so the sum of the spring constantk1 of each first spring SP1 and the spring constant k3 of each thirdspring SP3 is further increased to thereby make it possible to furtherincrease the resonance frequency fi of the first and second intermediatemembers 12 and 14 and to further decrease the resonance frequency ft ofthe damper device 10 as a whole. Thus, in the damper device of the firstalternative embodiment, as shown in FIG. 4, as compared with the damperdevice 10 of the embodiment, resonance between the first intermediatemember 12 and the second intermediate member 14 may be caused to occurat the time when the rotation speed of the engine is relatively high,and the resonance of the damper device as a whole may be caused to occurat the time when the rotation speed of the engine before completion oflockup is relatively low.

As described above, the damper device 10 included in the fluidtransmission apparatus 1 of the embodiment includes the drive member 11to which power from the engine that serves as a motor is transmitted,the first intermediate member 12 to which power is transmitted from thedrive member 11 via the first springs SP1, the second intermediatemember 14 to which power is transmitted from the first intermediatemember 12 via the second springs SP2, and the driven member 15 to whichpower is transmitted from the second intermediate member 14 via thethird springs SP3. Then, in the damper device 10 of the embodiment, coilsprings are used as the first and second springs SP1 and SP2, and arcsprings that are arranged radially inward of the first and secondsprings SP1 and SP2 are used as the third springs SP3. In this way, thethird springs SP3, which are one of the plurality of serially arrangedsprings, are arc springs, so it is possible to provide long stroke (lowstiffness) for the damper device 10. In addition, the third springs SP3that are arc springs are arranged radially inward of the first andsecond springs SP1 and SP2 to reduce centrifugal force that acts on thethird springs SP3 to thereby reduce the hysteresis of the third springsSP3, that is, friction force that acts on the third springs SP3 during areduced load. By so doing, it is possible to appropriately maintain thevibration damping characteristic of the third springs SP3. Thus, in thedamper device 10 of the embodiment, it is possible to improve thevibration damping characteristic while providing long stroke using arcsprings.

Furthermore, in the damper device 10 of the embodiment, the stiffness ofeach first spring SP1 is set so as to be higher than the stiffness ofeach second spring SP2 and the stiffness of each third spring SP3. Thatis, when the stiffness of each first spring SP1 is set so as to behigher than the stiffness of each second spring SP2, this makes it easyto substantially integrate the first intermediate member 12 with thesecond intermediate member 14, and the resonance frequency fi of thefirst and second intermediate members 12 and 14 is increased by settingthe stiffness of each first spring SP1 so as to be relatively high, soit is possible to cause resonance between the first intermediate member12 and the second intermediate member 14 when the rotation speed of thedrive member 11 is relatively high, that is, when the rotation speed ofthe engine is relatively high, and torque (vibrating force) from theengine is relatively low. By so doing, it is possible to suppress anincrease in the vibration level of the damper device 10 as a whole dueto resonance between the first intermediate member 12 and the secondintermediate member 14. Then, when the stiffness of each first springSP1 is set so as to be higher than the stiffness of each third springSP3, the characteristic of the arc springs that are the third springsSP3 is utilized to improve the vibration damping characteristic whileproviding the long stroke (low stiffness) for the damper device 10, andit is possible to appropriately damp resonance between the firstintermediate member 12 and the second intermediate member 14 by thethird springs SP3.

In addition, the drive member 11 that constitutes the damper device 10of the embodiment is connected via the lock-up clutch mechanism 8 to thefront cover 3, which serves as the input member coupled to the engine,and the driven member 15 is coupled to the input shaft of thetransmission. That is, the above described damper device 10 uses arcsprings to provide the long stroke (low stiffness) and improve thevibration damping characteristic, and the damper device 10 is able tocause resonance between the first intermediate member 12 and the secondintermediate member 14 or decrease the resonance frequency of the damperdevice 10 as a whole when the rotation speed of the drive member 11 isrelatively high, that is, when the rotation speed of the engine isrelatively high, and torque (vibrating force) from the engine isrelatively low. Thus, by using the above damper device 10, when therotation speed of the engine is extremely low, it is possible to carryout lockup by the lock-up clutch mechanism 8, that is, couple the frontcover 3 to the input shaft of the transmission, while appropriatelyreducing transmission of vibrations from the front cover 3 to the inputshaft of the transmission.

Note that the above described fluid transmission apparatus 1 isconfigured as the torque converter that includes the pump impeller 4,the turbine runner 5 and the stator 6; instead, the fluid transmissionapparatus that includes the damper device according to the presentinvention may be configured as a fluid coupling that has no stator. Inaddition, the above described fluid transmission apparatus 1 may includea friction-type multiple disc lock-up clutch mechanism instead of thefriction-type single disc lock-up clutch mechanism 8.

Here, the correspondence relationship between major elements of theabove described embodiment, and the like, and major elements of theinvention described in the summary of the invention will be explained.That is, in the above described embodiment, and the like, the drivemember 11 to which power from the engine, which serves as a motor, istransmitted corresponds to the “input element”, the first springs SP1,which are coils springs, to which power is transmitted from the drivemember 11 correspond to the “first elastic body”, the first intermediatemember 12 to which power is transmitted from the first springs SP1corresponds to the “first intermediate element”, the second springs SP2,which are coil springs, to which power is transmitted from the firstintermediate member 12 correspond to the “second elastic body”, thesecond intermediate member 14 to which power is transmitted from thesecond springs SP2 corresponds to the “second intermediate element”, thethird springs SP3, which are arc springs, to which power is transmittedfrom the second intermediate member 14 correspond to the “third elasticbody”, and the driven member 15 to which power is transmitted from thethird springs SP3 corresponds to the output element.

However, the correspondence relationship between the major elements ofthe embodiment and the major elements of the invention described in thesummary of the invention is one example for specifically explaining amode in which the embodiment carries out the invention described in thesummary of the invention, so the correspondence relationship does notintend to limit the elements of the invention described in the summaryof the invention. That is, the embodiment is just one specific exampleof the invention described in the summary of the invention, and theinterpretation of the invention described in the summary of theinvention should be made on the basis of the description itself.

The mode for carrying out the present invention is described above withreference to the embodiment; however, the present invention is notlimited to the above embodiment, and, of course, may be modified intovarious forms without departing from the scope of the invention.

The present invention is usable in the manufacturing industry, or thelike, of a damper device.

1. A damper device comprising: an input element to which power from amotor is transmitted; a first elastic body to which power is transmittedfrom the input element; a first intermediate element to which power istransmitted from the first elastic body; a second elastic body to whichpower is transmitted from the first intermediate element; a secondintermediate element to which power is transmitted from the secondelastic body; a third elastic body to which power is transmitted fromthe second intermediate element; and an output element to which power istransmitted from the third elastic body, wherein the first and secondelastic bodies are coil springs, and the third elastic body is an arcspring that is arranged radially inward of the first and second elasticbodies.
 2. The damper device according to claim 1, wherein the inputelement has a contact portion that contacts with one end of the firstelastic body, the first intermediate element has a contact portion thatis arranged between the other end of the first elastic body and one endof the second elastic body adjacent to the first elastic body and thatcontacts with both, the second intermediate element has a contactportion that slidably supports the third elastic body and that contactswith the other end of the second elastic body and a contact portion thatcontacts with one end of the third elastic body, and the output elementhas a contact portion that contacts with the other end of the thirdelastic body.
 3. The damper device according to claim 1, wherein astiffness of the first elastic body is higher than stiffnesses of thesecond and third elastic bodies.
 4. The damper device according to claim1, wherein the input element is connected via a lock-up clutch to aninput member coupled to the motor, and the output element is coupled toan input shaft of a transmission.
 5. The damper device according toclaim 2, wherein a stiffness of the first elastic body is higher thanstiffnesses of the second and third elastic bodies.
 6. The damper deviceaccording to claim 5, wherein the input element is connected via alock-up clutch to an input member coupled to the motor, and the outputelement is coupled to an input shaft of a transmission.